This invention relate to a method for lining of inner surface of a pipe by blowing atomized epoxy resin paints into the pipe.
Water mains, water pipes of apartment-houses or water pipes of factories are made from metal pipes, especially from iron pipes in many cases.
Though iron pipes are cheap and tough, they are apt to rust. The rust gradually grows up in the pipe and becomes a big lump (scale) which decreases an effective sectional area of the pipe. On account of rust in the water pipe, city water become muddy and brown. It is inadequate for cooking, drinking or washing.
Some methods of eliminating such scales in pipes are already known.
For example the method of eliminating scales by pushing a shell-formed matter with pressurized water or air in a pipe is well known.
When scales are eliminated perfectly, the inner surface of the pipe is revived to a clean state. However if the pipe were used as it is, it would rust again. Therefore the inner surface of the pipe must be lined with an adequate rustproof paint immediately after eliminating scales.
The customary method for painting inner surfaces of pipes is simply a traditional painting method applied for external surfaces. Namely a painter passes a painting spray coupled with a long hose through a pipe and paints the inner surface thereof by pulling out the hose slowly.
An advantage of this method is that ready-made painting tools can be used. But it has three disadvantages.
Firstly it requires a hose longer than the pipe to be lined. Thus this method is incapable of use for lining a long pipe. Secondly it is available only for pipes with wide diameters because a spray must be passed through the pipes. In practice this method cannot be applied to a narrow pipe with a diameter less than 3 B (1 B means 1 inch). Thirdly this method requires a long time because the hose must be moved slowly in order to avoid irregular painting.
Water mains in housing developments can be painted by the customary method, as the width of water mains is generally 3 B (3 inches). However this method is not available for water pipes of houses because the water pipes are only 1/2 B (half inch) wide.
Of course newly-produced pipes are lined properly by some methods. A new pipe which is not installed in a city water system can be easily moved, rotated or heated.
One method of painting new tubes or pipes is an electrostatic painting method and the other is a heating adhesion method of plastic tubing.
In the electrostatic painting method, some paint is introduced into the tube which is rotating slowly and charged with electricity. The paint particles adhere by the electrostatic force to the inner surface of the tube.
In the heating adhesion method, a thermoplastic tube--for example of vinyl chloride--with a diameter slightly narrower than that of the iron pipe to be lined, is inserted in to the iron pipe and is heated. By the action of heat the thermoplastic tube adheres to the inner surface of the iron pipe.
Both methods are useful only to new, isolated straight tubes. But pipes which have bends or elbows cannot be lined by these methods, because a thermoplastic tube cannot pass through an iron pipe with bends or elbows, and a non-straight iron pipe cannot be uniformly rotated in a heating device.
Furthermore these methods are totally ineffective to pipes which have been installed in buildings or laid under ground, because these pipes cannot be rotated nor heated and have many bends or elbows.